Use ControlUtil#using() to handle RevWalk.

src/main/scala/util/ControlUtil.scala

@@ -1,6 +1,7 @@
 package util
 
 import org.eclipse.jgit.api.Git
+import org.eclipse.jgit.revwalk.DepthWalk.RevWalk
 
 /**
  * Provides control facilities.
@@ -22,10 +23,6 @@ object ControlUtil {
       }
     }
 
-  /**
-   * Use this method to use the Git object.
-   * Repository resources are released certainly after processing.
-   */
   def using[T](git: Git)(f: Git => T): T =
     try {
       f(git)
@@ -33,6 +30,13 @@ object ControlUtil {
       git.getRepository.close
     }
 
+  def using[T](revWalk: RevWalk)(f: RevWalk => T): T =
+    try {
+      f(revWalk)
+    } finally {
+      revWalk.release()
+    }
+
   def executeIf(condition: => Boolean)(action: => Unit): Boolean =
     if(condition){
       action